The present invention generally relates to an electrical sensing system for a vehicle shifting system. More particularly, the present invention relates to an electrical sensing system that senses the position of a shift lever.
In the early years of automobiles, most automobiles included manual shift transmissions where an operator separately controlled clutch disengagement/engagement, speed of shifting, and engine rpm (i.e., throttle operation) as part of the shifting process. Modern vehicles in the United States are predominately automatic shift transmissions, where an operator merely positions a shift lever in a selected gear position and then presses on an accelerator, while the vehicle systems automatically control the speed of clutch engagement and the timing of shifting. Specifically, in modern automatically shifted vehicles, the operator positions a shift lever in park, reverse, neutral, or drive. However, the act of positioning the shift lever in a selected gear position is totally separate from controlling the actual shifting process, such that it does not give an operator the control provided by manually shifted transmission systems. It is desirable to come up with a design that does not require drivers to learn how to shift a manual vehicle transmission, including learning how to operate a clutch pedal, a brake pedal, and an accelerator pedal while simultaneously shifting a shift lever. Further, it is desired to provide a system compatible with existing driving skills and control technologies, and to provide a system where the driver does not have to operate a clutch if he or she prefers not to do so. In short, it is desirable to give more control of the shifting process back to the vehicle driver, but it is desired to do so in a manner that does not force the driver to relearn how to operate the vehicle and that allows the driver to be as active or passive as he or she may want to be. It is also desirable to utilize technologies that are compatible with and that take full advantage of the electronic vehicle systems in modern vehicles.
In general, an automatic transmission selects the appropriate gear ratio without direct driver input. Existing automatic transmissions include a mechanical system, as well as an electronic control system. Such automatic transmissions consist of a series of mechanical sub-systems which accept rotational input from the engine and deliver it to the driving wheels. These sub-systems are sequential in that the output of the first system provides the input to the second system, and so on. The rotational output from the engine is connected via the crankshaft to the torque converter. The torque converter is a fluid coupling which transfers drive torque from the engine into the transmission. A fluid coupling is the preferred choice for this application as the rotational forces are transmitted through a fluid, rather than a fixed mechanical link. This enables some slipping in the couplings so that harsh engine vibrations and shocks are not transmitted down the driveline. A further effect is that, while the coupling is slipping, the transmitted torque is multiplied, hence the name of this component. This effect is useful in accelerating a vehicle from stationary (xe2x80x9claunch feelxe2x80x9d). The operation of the torque converter may be visualized as to the electric fans, face to face. As one fan is turned, the flow of air causes the second fan to rotate as well. In the case of a torque converter, the drive side is called the impeller and is connected directly to the engine crankshaft. The driven side is the turbine in which then provides the rotational input into the transmission. Modern torque converters may also include a lock-up clutch. A lock-up clutch is an internal mechanical feature which prevents the torque converter from slipping. The lock-up clutch is applied when the vehicle is at cruising speed to improve efficiency and fuel economy. Design of the torque converter is dependent on the engine characteristics. The torque converter must be able to handle the torque capacity and torsional stresses generated by the engine, while not generating too much heat. Vehicle driveability and launch feel is another important consideration.
Rotating elements within an automatic transmission are coupled by the series of clutches. By applying these clutches in specific combinations, the appropriate gears are selected to transmit the torque. The clutches and bands within the transmission are also referred to as the shifting elements. Their function is to couple the rotating elements within the transmission in order to drive or to hold the gears, and thereby achieve the different gear ratios. The shift elements are also important in controlling the shift quality, and can make the difference between a silky smooth gear shift or a harsh shift. Clutches are multiple-disc type units of automatic transmission which feature a series of friction plates stacked in parallel. When released, the individual plates are able to slip and rotate freely. When applied, the clutch pack is compressed by a servo piston forcing the individual plates to lock and rotate together. Thus, when the clutch is released rotating elements can turn independently. When a clutch is applied, rotating elements are coupled. Brake bands generally comprise a steel strap lined with a high-friction material. The strap wraps around a rotating cylinder, and permits free rotation of the cylinder when the band is released. Pressurized oil can be selectively supplied to a servo piston, thereby causing the band to wrap tightly around the cylinder and hold it stationary. Hence, brake bands are used to hold a rotating element stationary. During a shift, the clutches and bands are applied or released in combination to achieve a specific gear state. By regulating the oil pressure, the shift elements can be applied in a controlled manner such that torque is transferred smoothly.
The gear set is a mechanism of the mechanical system by which the input speed is reduced and the input torque is multiplied. One known arrangement includes planetary gears, which are axisymmetric about the centerline of the transmission. A typical arrangement in a modern automatic transmission is a xe2x80x9cRavigneauxxe2x80x9d gearset including one forward sun gear, one reverse sun gear, and one planet gear supporting three long planet pinions and three short planet pinions. The Ravigneaux gearset also includes one ring gear connected to the output shaft of the transmission. By alternately driving or holding the first three elements in combination, the ring gear/output shaft is driven at different speeds, and the different gear ratios are obtained. The output from the transmission is connected to the propeller shaft (or transfer case in a 4WD vehicle). The rotation of the propeller shaft is directed to the driving wheels by the differential.
In addition to the mechanical system including the torque converter, clutches and bands, and gear set described above, modern automatic transmissions often include an electronic control system that provide the xe2x80x9cbrainsxe2x80x9d of the transmission. The electronic control system determines when gear shifts are required and then controls the shift quality during the execution of a gear shift. The electronic control system typically includes an electronic control unit (ECU), and an electrohydraulic unit (valve body). The ECU is a microprocessor which may be integrated into the engine control module or housed in a xe2x80x9cstand alonexe2x80x9d module. It is usually located in the vehicle interior and connected to the transmission and other systems via a wiring loom. The ECU continuously monitors a series of input signals provided by sensors. The input signals may include vehicle road speed, engine speed (rpm), transmission oil temperature, throttle position, rate of throttle opening, gear lever position, and mode switch. The ECU processes the input signals according to a series of algorithms to determine the current driving condition and the appropriate gear state for the transmission. If the appropriate gear state is different from the current gear state, the ECU initiates the shift to the desired gear state. During the shift, the ECU also actuates the electrohydraulic control system to ensure smooth shift feel.
The electrohydraulic unit or valve body of an automatic transmission is a hydraulic control system driven by the electrical output of the ECU. In one form, the electrohydraulic unit consists of electrically operated solenoids and a series of mechanical valves assembled within a die-cast aluminum housing. The valves direct automatic transmission fluid (ATF) to different circuits in the transmission, thus activating the mechanical systems. The electrohydraulic unit forms part of the transmission hardware, and is housed in the transmission oil sump. The control system is highly sophisticated and integral to the correct operation of the transmission. It comprises a number of on/off solenoids which are used to toggle valves and control the gear state. The system also features one or more variable pressure solenoids (VPS) which modulate oil pressure corresponding to the current (electrical signal) from the ECU. The VPS is used to modulate pressure to the clutches during a shift, hence controlling the shift feel.
Some modern vehicles manufacturers are now specifying and/or designing shifting systems for automatic transmissions having an automatic shift mode (such as the well-known gear positions of xe2x80x9cpark,xe2x80x9d xe2x80x9creverse,xe2x80x9d xe2x80x9cneutral,xe2x80x9d and xe2x80x9cdrivexe2x80x9d in most existing automatic transmission vehicle shifters), but also having a manual shift mode (where the shifter is movable between forced xe2x80x9cupshiftxe2x80x9d and xe2x80x9cdownshiftxe2x80x9d positions, or where the shifter is movable between a forced fourth gear, a forced third gear, a forced second gear, and a forced first gear). These arrangements give some control back to a driver by allowing the driver to force certain gear changes in automatic transmissions, but they do not give an operator the xe2x80x9ctotalxe2x80x9d control and feel of early manual shifting systems, since these known systems do not allow the operator to directly affect or control the clutch, the speed of shifting, and the engine responses to same, as discussed above. For example, in known systems, clutch engagement and gear engagement is at best only indirectly affected by how hard a vehicle driver presses on the accelerator pedal of the vehicle. The driver does not directly control the clutch by any manipulation of a clutch pedal or clutch controller. The speed of shifting the shift lever into a gear position also has no direct effect on clutch operation, or engine/transmission parameters or vehicle operation.
In addition to the above, different vehicle operators prefer different xe2x80x9cfeelsxe2x80x9d of clutch engagement when shifting between gear positions. For example, some operators want a rugged, stiff xe2x80x9chard clutchxe2x80x9d feel as a shift lever is moved between gear positions, while others prefer a smooth, xe2x80x9csoft clutchxe2x80x9d feel. Operators similarly differ in their preferences for engine speed and performance when shifting. Importantly, a specific operator""s preferences may change over time, such as when a road is slippery with snow or ice, or when the road is dry and providing good traction. Vehicle manufacturers have attempted to provide different shifters and transmissions tailored for particular types of customers (e.g., sport car-type drivers or luxury car-type drivers) that customers can select from, and further have attempted to match shifters and transmissions to the types of customers expected to buy particular vehicle models. However, to our knowledge, vehicle manufacturers have not constructed a shifting system including a shifter that is variable and sensitive to shift behaviors of an operator as a shift lever is shifted, or that is adapted to make xe2x80x9creal timexe2x80x9d changes in shifting and vehicle operation as a result.
Most modern vehicles have shifters that include shift levers mechanically connected to a transmission such as by a Bowdan transmission cable or a rod-type mechanical linkage. This was done in part since mechanical connections were believed to be very reliable and trustworthy for the environment under a vehicle where a transmission is located. However, mechanically connected shift levers are expensive, relatively large, and include many parts. Also, the assembly of these shifters into vehicles is labor intensive and takes up valuable assembly space.
An improved system solving the aforementioned problems and having the aforementioned advantages is desired.
Accordingly, it is an aspect of the present invention to solve the above problems by providing an electrical sensing system for a shifter that provides not only information identifying the gear selected by the driver, but also information indicating the relative force applied to the shift lever. It is another aspect of the invention to provide a shifting mechanism that changes the smoothness or the hardness of the shift performed by the vehicle transmission based upon the force applied to the shift lever by the driver when shifting between gears. Still another aspect of the invention is to provide a shifter that outputs additional information from which the velocity of the shift lever may be derived by a transmission controller or a separate controller.
To achieve these and other aspects and advantages, the shifting system of the present invention comprises a shift lever movable between gear positions for operating a vehicle transmission, and a sensing device for sensing positions of the shift lever including at least one position that is intermediate the two gear positions, the sensing device generates an electrical output signal indicating movement of said shift lever between the two gear positions when the sensing device detects the presence of said shift lever at the at least one position.
Another aspect of the present invention is to provide an electrical sensing system for a shifting mechanism that enables the gear positions of the shifting mechanism to be reconfigured and customized after manufacture without requiring a change in hardware. To achieve this and other aspects and advantages, the electrical sensing system of the present invention comprises sensing means for sensing a position of the shift lever relative to the two-dimensional plane and for generating an electrical output signal representing the sensed position of said shift lever, and a controller for associating specific transmission gears with defined positions of the shift lever that are sensed by the sensing means. The controller preferably includes means for enabling an operator to select which transmission gears the controller associates with the defined positions.
These and other features and advantages of the present invention will be further understood and appreciated by those skilled in the art by reference to the following specification, claims and appended drawings.